Oscillating lever in a valve train of an internal-combustion engine

ABSTRACT

A rocker or swing arm in a valve train of an internal combustion engine has a bearing bore pivotally supporting the arm on a hollow axis located in a fixed position in the engine. The valve train has a camshaft with cams for causing the arm to pivot. A hydraulic valve lash compensation element that acts on the tappet of a gas exchange valve connects to the arm. A supply line is arranged in the arm, and a radial opening connecting the hollow interior space of the axis to the supply line is arranged in the axis in the region of the arm to deliver hydraulic means through the hollow axis to the lash compensation element. According to the invention, a A labyrinth seal (35) surrounding the hollow axis without contact is arranged on the arm at each axial end of the bearing bore. The bearing space of the arm is laterally sealed by this means.

FIELD OF THE INVENTION

The invention concerns a rocker arm or swing arm in a valve train of an internal combustion engine that has a bearing bore by means of which the arm is supported in a pivoting manner on a hollow axis located in a fixed position in the engine.

BACKGROUND OF THE INVENTION

Known from the document DE-OS 198 44 202 is a valve train of an internal combustion engine with a rocker arm, one end of which acts on the tappet of a gas exchange valve and the other end of which is supported on the cam of a camshaft with the interposition of a hydraulic valve lash compensation element. In its center region, the rocker arm has a bearing bore with which it is supported in a pivoting manner on an axis located in a fixed position. This bearing is a plain bearing. Consequently, without roller bearing support of the arm on the arm axis, a potential for reducing friction goes unused here.

Document DE-OS 197 41 078 shows rocker arms or swing arms of the type mentioned at the outset for the valve train of an internal combustion engine, with a hydraulic valve lash compensation element. Here too, the bearing support of an arm on the fixed axis in the engine is implemented not as a roller bearing but as a plain bearing, so that a potential for reducing friction that could be achieved with a roller bearing goes unused.

SUMMARY OF THE INVENTION

The object of the invention is to laterally seal the rocker arm or swing arm to its bearing bore without the friction that arises in operation being increased thereby.

This object is attained according to the invention by the means that a labyrinth seal surrounding the hollow axis without contact is arranged on the arm at each axial end of the bearing bore, by which means the bearing space of the arm is sealed laterally. The leakage from the arm is significantly reduced by the long seal gap in the labyrinth.

The valve train can have a camshaft with cams for producing the pivoting motion of the arm, with a hydraulic valve lash compensation element that is connected to the arm and that acts on the tappet of a gas exchange valve, wherein a supply line is arranged in the arm, and a radial opening connecting the hollow interior space of the axis to the supply line is arranged in the axis in the region of the arm, in order to deliver hydraulic means through the hollow axis to the valve lash compensation element.

If the rocker arm or swing arm is equipped with a hydraulic valve lash compensation element, it is necessary to ensure that a sufficient fluid pressure is maintained in supplying the compensation element with hydraulic means. This is necessary so that enough oil pressure is present for splash oil required for lubrication, when oil is used as the hydraulic means. The oil supply pressure of the hydraulic valve lash compensation element and the oil pressure for splash lubrication are kept adequately high by means of the long seal gap of the labyrinth seal.

E105252 [and on all subsequent pages]

The arm can be provided in its bearing bore with a roller bearing, with which it is supported in a pivoting manner on the hollow axis. The valve friction can be reduced measurably by a roller bearing at the rocker arm or swing arm axis, for example by approximately 15 to 20 percent.

The arm can also optionally be equipped with a mechanical rocker arm insert or a mechanical rocker arm adjusting screw.

The roller bearing is chiefly implemented in a double row design, so that oil transfer from the rocker arm or swing arm axis to the hydraulic rocker arm insert or to the mechanical rocker arm insert or rocker arm adjusting screw is always ensured.

The roller bearing can be provided with a cage guiding the rollers, in the center of which is located at least one transfer opening for hydraulic means connected to the radial opening of the axis. In addition, possible alignment errors of the bearing bore with respect to the rocker arm or swing arm axis are compensated by a double-row design of the roller bearing.

With the invention, it is possible to use roller bearings for supporting rocker arms or swing arms without impairing the function of the hydraulic valve lash compensation element or the lubrication of the mechanical rocker arm insert or mechanical rocker arm adjusting screw.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is represented in the drawings and is described below in detail in comparison with arms for valve trains according to the previously known prior art. Shown are:

FIG. 1 a rocker arm according to the invention in longitudinal cross-section;

FIG. 2 a perspective view of the rocker arm;

FIG. 3 a perspective view of a portion of the rocker arm cut away along the longitudinal axis of the bearing bore,

FIGS. 4-7 partial longitudinal cross-sectional views of a rocker arm with installed valve lash compensation element and of a swing arm, as well as a representation of the contact region of the compensating element with one end of a valve tappet, according to the prior art;

FIG. 8 a longitudinal cross-section of a valve train installed in an internal combustion engine with a rocker arm, according to the prior art.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 4 through 7 show arms 1 of the type mentioned at the outset. In FIG. 4, the arm 1 is a rocker arm, while in FIGS. 5 and 6, the arm 1 is a swing arm. Each arm 1 has a bearing bore 2 with which it surrounds an axis 3 so as to be supported in a pivoting manner. This bearing is implemented as a plain bearing.

The axis 3 has a supply line 6 for hydraulic means. A hydraulic valve lash compensation element 5 is located in the region of one end 4 of the arm 1. The contact region 9 of said valve lash compensation element sits on one end 10 of the tappet 11 of a gas exchange valve.

A first radial bore 7 extends from the supply line 6 of the axis 3 for delivering the hydraulic means to the valve lash compensation element 5. A second radial bore 8 is located in the axis 3 for splash lubrication of the contact region 9. In the enclosing arm 1, a path 12 is used to transport hydraulic means to the valve lash compensation element 5, and another path 13 is used for splash application to the contact region 9.

A valve train 14 shown in FIG. 8 is built into an internal combustion engine 15 with a hydraulic valve lash compensation element 16, which is designed as a cylindrical cam follower and can be displaced at one axial end by the cam 17 of a camshaft. At its other axial end, the cam follower has a contact surface 18 on which the bottom end 19 of a valve lifter 20 rests. The displacement of the cam follower caused by the cam 17 is transmitted by the valve lifter 20 at its top end to an end region of a rocker arm 21.

In its center region, the arm 21 is supported on a hollow axis 23 by a bearing bore 22 so that it can pivot about the axis 23. The axis 23 is fixed in position in the cylinder head of the internal combustion engine 15. Here too, the support of the rocker arm 21 is implemented as a plain bearing. At its other end facing away from the valve lifter 20, the rocker arm 21 acts on the tappet 24 of a gas exchange valve. A hydraulic means is directed out of the concentric bore of the hollow axis 23 through a supply line arranged in the rocker arm 21 and through a supply line 25 arranged in the valve lifter 20 into the valve lash compensation element 16.

The arm 26 according to the invention shown in FIGS. 1 to 3 is implemented as a rocker arm and has a bearing bore 27 in its center region. An inserted hydraulic valve lash compensation element 28 is located at one end of the arm 26, while the other end is provided with a mechanical arm insert 29.

For pivoting support of the arm 26 on a fixed hollow axis, a cage 30 of a roller bearing 31 with rollers 32 implemented as needles is inserted in the bearing bore 27. A supply line 33 is arranged in the arm 26 for delivering oil as hydraulic means from the hollow axis surrounded by the cage 30 to the valve lash compensation element 28. In this supply line, the oil flows from the hollow axis through its radial opening and at least one transfer opening 34 of the cage 30.

According to the invention, the space of the bearing bore 27 of the arm 26 in which the roller bearing 31 is located is sealed with a labyrinth seal 35 at each axial end. This seal is placed on the arm 26 and encloses the hollow axis in a non-contacting manner.

LIST OF REFERENCE CHARACTERS

1 arm

2 bearing bore

3 axis

4 end of arm

5 valve lash compensation element

6 supply line

7 first radial bore

8 second radial bore

9 contact region

10 end of tappet

11 tappet

12 path

13 path

14 valve train

15 internal combustion engine

16 valve lash compensation element

17 cam

18 contact surface

19 bottom end

20 valve lifter

21 rocker arm

22 bearing bore

23 axis

24 tappet

25 supply line

26 arm

27 bearing bore

28 valve lash compensation element

29 arm insert

30 cage

31 roller bearing

32 roller

33 supply line

34 transfer opening

35 labyrinth seal 

1. Rocker arm or swing arm in a valve train of an internal combustion engine, having a bearing bore (27) by means of which the arm is supported in a pivoting manner on a hollow axis located in a fixed position in the engine, characterized in that a labyrinth seal (35) surrounding the hollow axis without contact is arranged on the arm (26) at each axial end of the bearing bore (27), by which means the bearing space of the arm (26) is laterally sealed.
 2. Arm according to claim 1, characterized in that the valve train has a camshaft with cams for producing the pivoting motion of the arm (26), with a hydraulic valve lash compensation element (28) that is connected to the arm (26) and that acts on the tappet of a gas exchange valve, wherein a supply line (33) is arranged in the arm (26), and a radial opening connecting the hollow interior space of the axis to the supply line (33) is arranged in the axis in the region of the arm (26), in order to deliver hydraulic means through the hollow axis to the valve lash compensation element (28).
 3. Arm according to claim 2, characterized in that it has a roller bearing (31) in its bearing bore (27) with which it is supported on the hollow axis in a pivoting manner.
 4. Arm according to claim 3, characterized in that the roller bearing (31) is of single-row design.
 5. Arm according to claim 3, characterized in that the roller bearing (31) is of multi-row design.
 6. Arm according to claim 5, characterized in that the roller bearing (31) is of double-row design with a cage (30) guiding the rollers (32), in the center of which cage is located at least one transfer opening (34) for hydraulic means connected to the radial opening of the axis.
 7. Arm according to claim 2, characterized in that it is implemented as a rocker arm in which the valve lash compensation element (28) is located at one end and the bearing bore (27) is located in the center region.
 8. Arm according to claim 2, characterized in that it is implemented as a swing arm in which the valve lash compensation element (28) is located at one end and the bearing bore is located at the other end.
 9. Arm according to claim 2, characterized in that a mechanical arm insert (29) or arm adjusting screw is connected to the arm (26) at one end. 